Hakuin used to tell his pupils about an old woman who had a teashop,
praising her understanding of Zen. The pupils refused to believe what he
told them and would go to the teashop to find out for themselves.

Whenever the woman saw them coming she could tell at once whether they
had come for tea or to look into her grasp of Zen. In the former case, she
would server them graciously. In the latter, she would beckon to the
pupils to come behind her screen. The instant they obeyed, she would
strike them with a fire-poker.